The present invention relates to a digital signal forming method, disc recording media using the same and reproducing method thereof and particularly to a digital signal forming method suitable for information recording media, disc recording media having recorded the digital signal formed with this method as the recording pits (marks) and the reproducing method thereof.
As an example of disc recording media for converting a recording information to a digital signal suitable for recording media and then recording such digital signal as the recording pits (marks) on the media, a DVD (Digital Versatile Disc) may be listed. A method of forming such digital signal is described in the article “Data Compression and Digital Modulation”, NIKKEI ELECTRONICS BOOKS, 1998, pp. 119 to 123. In this reference, 2064 bytes where an addition information pieces such as sector ID number are added to the recording information amount in unit of 2048 bytes (number of bytes up to main data 12 from the main data 1) after scramble process are defined as one sector data, these sector data are in the form of 172 bytes×12 lines. In the allocation in unit of 172 bytes×12 lines×16 sectors for 16 sector data, the PO correction code of 16 bytes are added in the vertical direction as the external code, and the PI correction code of 10 bytes are also added in the lateral direction including the PO correction code as the internal code, and the correction block of (172+10) bytes×(12 lines×16 sectors+16 lines) is formed. Moreover, the interleave allocation is formed by interleaving in unit of one line the line data of the correction block. After modulation and framing process (to add a synchronization signal) from the heading line of the interleave allocation, generated digital signal is recorded as the recording pits (marks) along the tracks on the disc. At the time of reproducing, the original recording information can be reproduced by reproducing the recording pits (marks) using an optical head, then conducting detection of the frame synchronizing signal, demodulation process, recovery of the interleave allocation and then conducting the correction process for the error generated in the correction block with the PI, PO correction code. The PI correction code is used for correction of the random error included in unit of line from, while the PO correction code is used for correction of the burst error included in a plurality of line data.
The correction code, allocation format, modulation system, framing process are used in common for the recording signals to the DVD disc such as read-only disc (DVD-ROM), WORM(Write Once Recording Media) disc (DVD-R), re-writable disc (DVD-RW, DVD-RAM or the like) and the compatibility of digital signal process for recording and reproducing is assured.
A digital signal forming method of the related art will be explained with reference to FIG. 2.
FIGS. 2 illustrate allocation of data and codes for explaining the digital signal forming method on the occasion of recording information to a disc of the related art. FIG. 2(A) illustrates a recording information on a recording medium, while FIG. 2(B) illustrates a sector data, FIG. 2(C) illustrates a correction block and FIG. 2(D) illustrates an interleave allocation.
In these figures, the reference numeral 1 indicates a series of recording information (divided in unit of 2048 bytes) to be recorded to a recording medium; 2, a format of the sector data which is one of the recording unit to the recording medium The sector data 2 divides a series of recording information 1 in unit of 2048 bytes. The sector data 2 is formed of an additional information of 12 bytes for RSV (reservation) including the sector ID (Identification Data) indicating the physical recording position on the disc, IED (ID Error Detection Code) for correction of one byte to the sector ID and a copy inhibit flag information or the like and the EDC (Error Detecting Code) checking existence of error to the main data 1 to 12 of 2048 bytes recording information. Moreover, the allocation in total of 172 bytes×12 lines×16 sectors is formed by collecting 16 sector data 2. In this allocation of 172 bytes×12 lines×16 sectors, the correction block 3 is formed with addition of the error correction code to each series of vertical and lateral series in order to cover the burst error and random error resulting from scratch or dust on the disc during the reproducing of disc. Namely, the correction block 3 of 182 bytes×208 lines is formed by generating and adding the PI (outer-code parity) correction code of 16 bytes to the codes 12×16 bytes in the vertical direction and then the PI (inner-code parity) correction code of 10 bytes to the code of 172 bytes in the lateral direction. Moreover, in the correction block 3, the interleave allocation 4 can be obtained by conducting the interleave process in every line from the heading line in the allocation of the PO correction code in unit of allocation of the data of sector 15 from the data of sector 0 by 182 bytes×12 lines. In the interleave allocation 4, the PO correction code of one byte is allocated sequentially between sectors and the sector ID is allocated at the heading position of each sector. Each line of the sectors 0 to 15 is provided with a line of the data and PI correction code.
The ID number included in each sector after the interleave is given a series of continuous number and also continuous even at the adjacent sectors. Finally, the modulation process and framing process are performed to generate the adequate digital signal for recording as the recording pits (marks) on the disc.
In the case of reproducing of the recording information from a disc, the recording pits (marks) are read with an optical head and are then converted to a digital signal. Thereafter, after the frame synchronizing process and demodulating process are conducted in the inverse sequence of generation of the digital signal explained with reference to FIG. 2, the interleave allocation is recovered, for example, on a semiconductor memory and the error data included in the allocation is corrected by conducting the correction process through decoding of the PI, PO correction codes while releasing the interleave allocation. From the data series as the encoding object of the PI, PO correction codes in the correction block 3, the PI correction code corresponds to the random error correction which is occurred at random in the line data including the continuous recording information, while the PO correction code corresponds to the burst error correction which is occurred in the form of a burst for a plurality of lines of vertical series. Allocation, code length in the PI and PO series, number of additional bytes of the PI, PO correction codes, number of bytes (symbols) to be corrected, namely the correction capability is determined to realize sufficient correction capability for the error rate, scratch and dust during the disc reproducing.
A disc recording medium represented by the DVD is assumed in future to show more improvement of recording density of a recording medium and higher transfer rate for the purpose of longer-term recording and reproduction of video information and recording of higher definition video information in the higher transmission rate. As an example of the method to realize improvement in recording density and transfer rate, it is possible to form a track pitch to 1/m (m is a decimal number larger than 1) and a recording pit (mark) to 1/n (n is a decimal number larger than 1) on the disc of the related art or introduce the modulation system having higher encoding efficiency for generation of the digital signal. However, with improvement in the recording density, generation of burst error resulting from scratch or dust generated on the disc during the reproducing increases, and thereby readability of disc is lowered. Therefore, on the high density recording, it is essential to assure sufficient readability resistive to actual operation for scratch and dust, namely to improve the error correction capability for the digital signal to be recorded.
However, when only the number of correction codes is increased, the number of symbols that can be corrected is increased and the number of codes as the correction object and the number of correction codes to be generated are increased for improvement of error correcting capability, here rises problems that the correction code to realize error correction capability cannot be generated and redundant data having no relation to the recording information increases. Moreover, there rises also a problem that compatibility of signal process between the generation and reproduction processes of the recording signal for the current DVD is remarkably lowered.